气候变化对中国农林生物质能的区域影响研究

【作者】 马占云；

【导师】 林而达； 李怒云；

【作者基本信息】 首都师范大学 ， 自然地理学， 2009， 博士

【摘要】 气候是人类生存环境的基本组成部分,政府间气候变化专业委员会（IPCC）第四次评估报告（AR4）指出最近100年（1906²005年）地球表面平均温度上升了0.74（0.56⁰.92）℃。全球气候变化问题,不仅是科学问题、环境问题,而且是能源问题、经济问题和政治问题。在当前气候变化形势下,发展生物质能不仅有助于解决农村发展和农民生活问题,也有利于保护生态环境,保证国家能源安全,缓解能源危机。作为生物质能资源利用首先要清楚有多少资源量,分布如何。在2008年国务院办公厅下达的《关于加快推进农作物秸秆综合利用的意见》要求,摸清秸秆资源情况和利用现状,分析未来发展趋势。所以定量计算我国生物质能的资源量,分析气候变化对其的区域影响,并预测未来气候变化条件下的发展趋势,对我国中长期规划和发展目标的确定具有重要的意义。研究采用了统计资料分析、试验验证和模型模拟的方法对我国农业生物质能进行了现状和未来发展趋势的区域分析。在气象和统计年鉴资料的基础上分析了我国气候变化的事实,即温度和降水对我国水稻、玉米和小麦三大作物秸秆量的变化的影响;在FACE系统试验平台（Free-air CO₂ enrichment,FACE）基础上验证了CO₂浓度升高对冬小麦秸秆量和经济系数等指标的影响;利用CERES系列作物模型模拟了未来气候变化情景下主要农作物秸秆的变化趋势;还研究了气候变化对林业生物质能的影响;进一步分析了中国生物质能开发利用情况。结果表明:（1）我国气温增暖明显,而降水呈微小的下降趋势。我国过去50年的增暖主要发生在80年代中期以后,特别是90年代,增温异常明显。我国年平均气温呈现明显的上升趋势,全国2004年的平均温度比1974年增加1.09℃,除了1986年及其以前的温度低于平均温度以外,1987年到2004年各年平均温度均高于此31年的平均温度。（2）气候变化对秸秆量的影响。利用农业统计年鉴（1983²005）,通过经济系数和作物产量计算得出1982²004年我国三大主要粮食作物秸秆资源量,水稻秸秆年均产量为1.814×10⁸t,小麦年均总产为1.636×10⁸t,玉米年均总产量为1.206×10⁸t。我国三大作物秸秆总量呈增加的趋势,当前随着温度的升高,水稻和小麦秸秆产量呈减少趋势,玉米秸秆产量呈增加的趋势,但是我国各区域变化趋势不同。温度升高对各区域的主要作物秸秆产量的影响以增加为主,且都通过了0.01水平的相关性检验,但降水则只有部分地区通过检验。可见温度对作物秸秆产量的影响比降水的影响大。（3）通过CO₂浓度升高对冬小麦的影响试验（FACE）可以得出,CO₂浓度升高对冬小麦的株高、生物量和秸秆量的影响大致相同,结果都是促进作用,高于对照值。而且使冬小麦的经济系数减小,即增加了秸秆在生物量中的比重。CO₂浓度升高条件下,对于两个品种平均的经济系数减小,对照的平均经济系数为0.40,高CO₂浓度下的平均经济系数减小为0.38。这符合国际FACE试验的结果规律,在CO₂浓度升高的作用下,作物生长向着植株越来越高的方向发展。而且对于试验的对照条件和FACE条件相比则符合经济系数和株高成反比的规律,在FACE条件下经济系数减小,株高明显增高。（4）在IPCC气候变化SRES（Special Report on Emissions Scenarios）排放情景A2和B2下,在考虑了CO₂肥效作用的影响下,利用作物模型模拟了未来主要农作物秸秆量的变化趋势,在A2情景下以减少为主,平均单位面积秸秆量在2020s增加0.13%,2050s和2080s分别减少0.24%和2.08%。B2情景增加,特别是小麦呈现幅度较大的增加,三大作物总平均单位面积秸秆量增加率分别为8.64%、11.99%和18.10%。且两个情景都是随时间变幅增大。（5）在保证粮食安全的前提下,农作物秸秆和非农林能源作物作为能源利用可进一步加强。在保证粮食安全的前提下,农作物秸秆和能源作物则是生物质能的重要原料,我国农作物秸秆资源丰富,仅三大粮食作物每年就可以产生5×10⁸t左右的秸秆,除了部分还田以保持土壤碳含量外,尚有可用于生物能源的部分,此外我国尚有近1×10⁸ hm²宜农、宜林荒山荒地,可用于发展能源农业和能源林业,而且我国能源农林业物种资源非常丰富,农业主要有木薯、甘蔗、甜高粱、油菜、花生、向日葵等,林业有漆树科的黄连木,无患子科的文冠果,大戟科的小桐子,山茱萸科的光皮树等,以此为原料可以进一步加强我国的生物液体燃料等的生物质能利用方式。（6）从农民增收的角度,农作物秸秆和非农经济林综合利用可进一步发展。生物质能的开发利用对解决“三农”问题有重要的作用,农作物秸秆和非农经济林综合利用能进一步增加农民收入。在把农作物秸秆变“废”为“宝”的生物质能利用,收购农民手中的作物秸秆即可增加农民收入。另外生物质能的利用可以创造就业机会增加农民收入,而且以户用沼气为纽带的综合利用模式在很大程度上增加了农民的收入,在国家资金和政策的大力支持下,户用沼气和大中型沼气工程发展迅速。另外我国约有经济林2140×10⁴hm²,其中木本油料树总面积超过400×10⁴hm²,油料树的果实产量每年在200×104t以上,可作为生物柴油的原料。其中对林木、林果、林副产品等林业资源的经营管理,可以增加林农的收入。（7）从环境保护角度,保证足够的秸秆还田量以后,农林生物质替代能源工程可作为新农村的基本设施建设纳入国家计划。农作物秸秆用于生物质能利用减少了露天焚烧,减少了环境污染,在生物质能利用中提高了利用效率,较传统的直接燃料燃烧即节约了能源又改善了农村居民的生活环境和生态环境。而且秸秆还田可以减少CO₂和SO₂的排放,增加土壤碳,为保护环境和减缓气候变暖做出贡献。（8）本文利用meta分析方法分析了我国近年来秸秆还田的文献资料,估算出我国秸秆还田量最适宜为4.78t/hm²,理论上我国作物适宜秸秆还田的数量占总秸秆资源总量的87%。我国三大作物秸秆实际的直接还田量仅为0.61⁰.81×10⁸t,占其总产的13%¹7%。利用水稻、玉米和小麦秸秆的可收集利用系数,估算我国三大主要农作物秸秆资源可收集利用量为3.715×10⁸t,占三大作物总秸秆产量的79.76%。而在我国三大作物年均秸秆生物质能可利用量估计为0.817¹.485×10⁸t。根据模拟未来气候变化A2和B2情景下秸秆量变化率,在假设种植面积不变的情况下,总产的变化率与相同,符合我国中长期规划的B2情景下的主要作物秸秆产量和生物质能可利用量都是随着时间而增加的,到2050s可以达到0.92¹.66×10⁸t以上。更多还原

【Abstract】 Climate is an important part of environments that human beings depend on. As the AR4 of IPCC reported, in the resent 100 years, the global surface temperature has increased by 0.74（0.56-0.92）℃。Climate change is not only scientific and environmental issue but also energy, economic and socio-political issues. Under the climate change conditions, development of bioenergy can contribute the development of rural area of China and improve the livelihoods of farmers, as well as protect eco-environment, secure energy supply of China and alleviate energy crises. An understanding of the energy resources and distribution is a prerequisite for utilization of bio-energy. Therefore, in 2008 General Office of the State Council of the People’s Republic of China released the document on accelerating the promotion of comprehensive utilization of crop straw to find out the situation of crop straw resource, current utilization of crop straw and its future development trends. This will provide fundamental information for comprehensive utilization of crop straw and assessment of agriculture resource, as well as provide evidences for the constitution of special planning of comprehensive utilization of crop straw and resource utilization and evaluation of crop straw. So quantifying the resource reserve of bioenergy, analyzing the impacts of climate change on resource reserve of bioenergy and predicting its development trends under future climate will contribute the medium and long term development plan of energy of China.In this study, Chinese bioenergy from agriculture and forestry under current and future climate was investigated using the methods of statistical analysis, evaluation of field experiment and model simulation. Based on the meteorology records and statistical information of China, climate change in China, changes in rice straw, maize straw and wheat straw and the impacts of temperature and rainfall on crop straw were analyzed. The effect elevated CO₂ concentration on wheat straw was evaluated through Free-air CO₂ enrichment （FACE） experiment. The CERES crop model was used to simulate future trends in the main crop straw of China under the future climate scenarios. Also the impacts of change on bioenergy from forestry were assessed, which will provide evidence for development and utilization of bioenergy of China. The main conclusions of this study are:（1） In China, the air surface temperature increased significantly, and there is a slight decrease in rainfall. The warming up period in China begins at the middle of the 1970s and becomes significant in 1990s for the last 50 years. The warming trend of the average temperature of China is obvious. The average temperature of 2004 is 1.09℃higher than 1974. With the exception of 1986, the average temperature of the other years （1987-2004） is higher than the average temperature of 31 years（1974-2004）.（2）The effect of climate change on the straw production. Based on the Yearbook of Agricultural Statistics of China （1983-2005）, this paper gets the three major crop straw productions by computing the economic coefficient and the crop yield of per unit. The annual average yields of the three major crops are 1.814×10⁸t （rice）, 1.636×10⁸t （wheat） and 1.206×10⁸t （maize）. The total amounts of China’s three major crop straw productions are increasing while the rice and the wheat are decreasing. With increasing temperature, rice and wheat straw production decreases while the maize straw production has an increasing trend. But the trend is varies in different regions of China. The increasing temperature leads to the increasing trend of major crop straw and it has passed the 0.01 level of correlation test. But only parts of the precipitation pass the test. It shows that the temperature plays an important part on the effect of crop straw yield than the precipitation.（3）It can be drawn through the increased CO₂ concentration on the impact of winter wheat experiment （FACE） that the increased CO₂ concentration can promote the plant height, biomass and the straw field of the winter wheat based on the control value. The economic coefficient of the winter wheat decreases which means an increase of straw field. Under the conditions of increased CO₂ concentration, the average economic coefficient of the two varieties decreases. The average economic coefficient is 0.38 under the high CO₂ concentration while the control value is 0.40. This is in line with the international law of FACE results that in the role of increased CO₂ concentration, the crop plant is getting higher and higher. For the control test conditions and compared FACE conditions, the economic coefficient is inversely proportional to the plant height which means the economic coefficient decreases when the plant height increased significantly under the conditions of the FACE experiment.（4）Under the emission scenarios A2 and B2 of the IPCC climate change SRES （Special Report on Emissions Scenarios）, taking the fertilizer effect of the CO₂ into account, this paper uses the crop models to simulate the future change of the trends of major crop straw production. Under the A2 scenario, the production reduced in general. The average per unit production of the straw increased 0.13% in the 2020s and decreased 0.24 and 2.08% in the 2050s and 2080s. Under the B2 scenario, wheat production increased significantly and the per unit production of crops straw of the three major crops increased respectively by 8.64%、11.99% and 18.10%. And the amplitude is increasing with time under the two scenarios.（5） Based on the security of food supply of China, the energy utilization of crop strews and no bio-energy crop can be further strengthened.In China, crop strews and energy crops are the main resource of bioenergy under the condition of secure food safe. There are lots of resource of crop strew, and only the main tree food crop can produce about 0.5 billion ton strew, which can maintain soil carbon and was used as the resource of bioenergy. In addition, there are about 0.1 billion hm2 waste hills and and that is suitable for farming or forestry can be used for the development of agriculture and forestry energy. The main energy source crops in China are cassava、sugarcane、sweet sorghum、rape、beet、groundnut、sunflower and so on. The main forestry energy sources are Pistacia chinensi、Xanthoceras sorbifolia、Jatropha curcasL、Cornusw ilsoniana W anger and so on. All these can be used as energy resource of China to strengthen utilization of bio-liquid energy.（6） The comprehensive utilization of crop strews and non agriculture economic forestry can be further developed to increase the income of farmer.The development and utilization of bioenergy can resolve the problem from agriculture famer, rural area of China. And it can further improve the income of farmer by altering the crop strews into useful bioenergy and saling crop strew, in addition increase the work opportunity for the farmer. The comprehensive utilization pattern with biogas engineering as link such as the eco-agricultural model （Four-in-One）in North China, which can greatly improve the income of farmer. Also, there is great development in household biogas and large and medium biogas engineering under the support of governmental funding and policy. There is 21.4 million hm2 economic forestry and the total area of woody oil plant exceeds 4 million hm2. The fruit production of woody oil plant is above 2 million ton per year, which can be used as resource of bio-diesel oil. Also, the management of forestry resource such as woods, fruit tree and Forestry by-products can enhance the income of agriculture and forestry.（7） From the view of environment protection, alternative bioenergy engineering from agriculture and forestry can be brought into line with the state plan when enough crop strew is return to the field.Utilization of bioenergy from crop strew can reduce the burning of strew, hence reduce the environment pollution and improve the use efficiency of bioenergy. Compared with the traditional burning of energy, bioenergy can save energy use and improve life environment and eco-environment of rural area of China. Fertilizing soil through straw returned into field can reduce emission of CO₂ and SO₂ and increase soil carbon, which would contribute the protection of environment and relieve the warming.（8）In this study, meta method was used to analyze the amount of straw returned into field based on the literature, and it is estimated that in China the optimal amount of straw returned into field is 4.78t/hm2. In theory, the amount of crop straw returned into field only accounts for 87% of total strew resource of China. The main three crop straw returned into field only 0.61⁰.81×10⁸t, which accounts for 13¹7% of total strew resource. Under the A2 and B2 climate scenarios, the change in crop strew yield and the total strew production is similar to that of current climate on the assumption that the planting area is same. Under the B2 climate scenario, the production of main crop strew and utilization of bioenergy will increase over time, and it will reach above 0.92¹.66×10⁸t billion t by 2050s更多还原